1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing spools of photographic film cassettes. Particularly the present invention relates to a method and apparatus for manufacturing photographic film cassettes having a spool wherein thin flanges are reliably mounted on a spool core. The present disclosure is based on the disclosure of Japanese Patent Appln. No. 4-166420 filed Jun. 24, 1992.
2. Description of the Related Art
U.S. Pat. No. 4,423,943 discloses a photographic film cassette which contains a roll of photographic film wound on a spool such that a film leader does not initially protrude from a cassette housing and may be advanced to an outside of the cassette housing through a film passage slit by rotating the spool.
In such a photographic film cassette, one of the most significant problems is how to prevent "clock-springing" or loosening of the film roll wound on the spool. To solve this problem, European Patent 0406815A2 (which corresponds to Japanese Laid-Open Patent Application 3037645) and U.S. Pat. Nos. 4,834,306 and 4,848,693 disclose a photographic film cassette wherein a spool has flanges on opposite ends of a spool core and rims of the flanges are deformed toward the outer periphery of a film roll coiled about the spool core to cover opposite ends of the film roll. In this way, the loosening of the film roll is prevented.
For easy deformation, the flanges are favorably formed from a thin flexible material, such as flexible plastics. However, it has been difficult to automatically form thin flanges and mount them on the spool core. If the thin flanges are formed by molding, the flanges cannot be easily removed from the mold due to electrostatic attraction. This reduces the manufacturing efficiency. Furthermore, if a robotic arm or the like is used to mount the flanges on the spool core, it is necessary to control the grasping power of the mechanical hand thereof with extremely high accuracy, due to the fragility of the flanges. Therefore, cassettes having thin flanges have previously been expensive to manufacture.